Maybe a case of Rosarita refrieds, a six-pack of Coke, and some jumping jacks....... Actually, I would think if it was strictly for show, you could rig up something better than using unburned fuel from your exhaust pipe. Stunt folks have been setting up stuff like that for the movies for years...... The temptation to show it off one night in a parking lot, combined with Murphy's Law, would probably result in some issues. I remember some years back a friend of mine had a Mazda with a rotary engine. For some reason it was pumping a lot of unburned fuel down the exhaust pipe. It would routinely blast out shotgun sounding explosions from the tail pipe. One day his cat exploded. I'm guessing it got too hot and trapped some of the gasses. Sounded cool though.